1. Field of the Invention
The present invention pertains to I.V. pumps for administering parenteral liquids in a controlled manner to a patient, and more particularly, it pertains to disposable I.V. pump cassettes which contain a small pumping chamber and a reciprocable piston or plunger for pumping liquid from the chamber and which are adapted to be inserted into pump driver mechanisms wherein the reciprocation of the piston or plunger can be controlled and monitored so as to achieve the desired delivery rate to the patient.
2.Description of the Prior Art
The intravenous delivery of fluids, such as nutrient solutions, has been a conventional and wide-spread practice in hospitals throughout the world for many years. Until relatively recently, such devices were typically of the gravimetric flow type wherein a bottle or bag containing the I.V. liquid was hung upon a pole or the like at an elevated location with tubing extending therefrom to a needle to be inserted into the vein of the patient. More recently, I.V. pumps have gained widespread acceptance since they are able to deliver fluids under very accurate and tightly controlled conditions so that potent medications or the like can be delivered intravenously to a patient wherein deviations from the desired delivery rate could have serious consequences.
In the conventional I.V. pumping apparatus now in use, there will typically be provided an I.V. pump driver mechanism including a variety of operating controls. The pump driver mechanism will be adapted to accept a disposable cassette containing the basic pumping chamber. The cassette, which is typically designed for one use only, is relatively small and must be economically manufactured to reduce its cost since it is designed to be disposable. The cassette will typically be activated by a reciprocatory driving device of the pump driver mechanism and will have tubing connections leading to the supply container and an intravenous set or the like for delivery of the I.V. fluids to the patient.
One typical prior art I.V. pump cassette is shown in U.S. Pat. No. 4,336,800 to Pastrone. As shown in this patent, the rigid plastic cassette comprises a positive displacement pumping chamber the volume of which is controlled by a diaphragm which is attached to a plunger extending upwardly from the body of the cassette. An inlet, for connection to appropriate tubing, is provided at the upper end of the cassette, and similarly, an outlet for connection to outlet tubing is provided at the lower end of the cassette. Extending laterally in a general horizontal plane is a supporting portion which is used to support the cassette in a pump driver mechanism and permit it to be clamped therein in an operable position by clamp members of the driver mechanism which are received in recesses on opposed sides of the support portion.